In the manufacture of paper on continuous papermaking machines, a web of paper is formed from an aqueous suspension of fibers on a traveling mesh wire or fabric and water drains by gravity and vacuum suction through the fabric. The web is then transferred to the pressing section where more water is removed by dry felt and pressure. The web next enters the dryer section where steam heated dryers and hot air completes the drying process. The wire or fabric and felt are commonly referred to as papermaking clothing which is conditioned (or cleaned) periodically and replaced as required. Substandard clothing leads to poor web formation on the machine which ultimately results in lower quality paper products exhibiting streaks, pinholes and poor mechanical and optical properties.
Techniques for regulating papermaking by monitoring the condition of the felt and/or affecting the moisture level of the felt are known. For example, EP 2198278 describes infrared measurement of the paper machine clothing condition to control paper production. U.S. Pat. No. 7,811,417 describes a cross-direction actuator system for maintaining the moisture level on press felt in order to affect the moisture content in the sheet of paper produced. EP 1342839 describes measuring the hardness or compactness of clothing to determine its condition and performance. EP 1329551 describes monitoring the cross-direction dewatering profile in the wet section to determine when replacement of the felt was necessary.
The average felt life is approximately 40 to 45 days and the average wire life is approximately 90 to 100 days, with both being dependent on the type of paper machine and nature of raw material processed. To avoid interruptions and downtime caused by unexpected clothing breakage during production, papermakers often replace the felt and wire more frequently than is required. In addition, papermakers will change the grades of paper being produced in order to reduce the likelihood of breakage. For instance, a changeover from a lower basis weight paper to a higher basis weight paper can be implemented as the wire fabric becomes impregnated with fiber and debris. The basis weight is the paper's weight per area and is typically designated in the industry by grams per square meter (gsm). Unscheduled changeovers generate excess inventory of unplanned paper grades.